In most cellular communication networks there are cells, which broadcast signals, which reaches far beyond the desired planned cell border. This may be due to a number of different reasons, e.g. that the Radio Base Station (RBS) associated with the cell is located on a hill or on a high building. It could also be due to insufficient optimization, e.g. of the transmit power used for transmission of signals from the RBS. Further, it could be due to newly integrated sites (RBSs/cells), which are not yet totally optimized.
Since the signals of such cells reach beyond the cell border, mobile terminals located at a substantial distance, i.e. far from the cell may receive a strong signal from such a cell at certain locations. This may lead to that the mobile terminal performs a call on such a distant cell, rather than on a cell that is located geographically closer to the mobile terminal, which is undesired. Such cells, which are located further away from a mobile terminal than a predefined threshold, on which cells it is undesired that a mobile terminal performs a call, will henceforth be denoted ‘distant cells’. Even though connection to a distant cell is possible, such a connection entails a high risk for so-called drop calls, and is therefore undesired. A drop call is, as the name indicates, a call, which is dropped or lost in an unintentional way.
Calls that are performed on distant cells may be detected by optimization engineers by checking some performance counters on the OSS (Operating Sub System) or via signaling message analysis after an increase in the number of drop calls. In order to solve the problem of calls performed on distant cells, the optimization engineers would probably adjust the antenna tilt of the antennas associated with the undesired cell or they might reduce the strength of the cell radio signal power. However, this type of solutions are slow and inefficient.